Compatibilised polyolefin compositions

Compatibilised polyolefin compositions combining the positive properties of their respective components by using an olefinic di- or triblock copolymer as compatibiliser to generate a finely dispersed phase structure in the molten state and to improve adhesion between the blend components in the solid state, while not compromising processability of the polyolefin composition

Synthesis and Electronic Structure Determination of Uranium(VI) Ligand Radical Complexes

   Pentagonal bipyramidal uranyl complexes of salen ligands, N,N’-bis(3-tert-butyl-(5R)-salicylidene)-1,2-phenylenediamine, in which R = tBu (1a), OMe (1b), and NMe2 (1c), were prepared and the electronic structure of the one-electron oxidized species [1a-c]+ were investigated in solution. The solid-state structures of 1a and 1b were solved by X-ray crystallography, and in the case of 1b an asymmetric UO22+ unit was found due to an intermolecular hydrogen bonding interaction. Electrochemical investigation of 1a-c by cyclic voltammetry showed that each complex exhibited at least one quasi-reversible redox process assigned to the oxidation of the phenolate moieties to phenoxyl radicals. The trend in redox potentials matches the electron-donating ability of the para-phenolate substituents. The electron paramagnetic resonance spectra of cations [1a-c]+ exhibited gav values of 1.997, 1.999, and 1.995, respectively, reflecting the ligand radical character of the oxidized forms, and in addition, spin-orbit coupling to the uranium centre. Chemical oxidation as monitored by ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy afforded the one-electron oxidized species. Weak low energy intra-ligand charge transfer (CT) transitions were observed for [1a-c]+ indicating localization of the ligand radical to form a phenolate / phenoxyl radical species. Further analysis using density functional theory (DFT) calculations predicted a localized phenoxyl radical for [1a-c]+ with a small but significant contribution of the phenylenediamine unit to the spin density. Time-dependent DFT (TD-DFT) calculations provided further insight into the nature of the low energy transitions, predicting both phenolate to phenoxyl intervalence charge transfer (IVCT) and phenylenediamine to phenoxyl CT character. Overall, [1a-c]+ are determined to be relatively localized ligand radical complexes, in which localization is enhanced as the electron donating ability of the para-phenolate substituents is increased (NMe2 > OMe > tBu)

Classification of current anticancer immunotherapies

During the past decades, anticancer immunotherapy has evolved from a promising therapeutic option to a robust clinical reality. Many immunotherapeutic regimens are now approved by the US Food and Drug Administration and the European Medicines Agency for use in cancer patients, and many others are being investigated as standalone therapeutic interventions or combined with conventional treatments in clinical studies. Immunotherapies may be subdivided into “passive” and “active” based on their ability to engage the host immune system against cancer. Since the anticancer activity of most passive immunotherapeutics (including tumor-targeting monoclonal antibodies) also relies on the host immune system, this classification does not properly reflect the complexity of the drug-host-tumor interaction. Alternatively, anticancer immunotherapeutics can be classified according to their antigen specificity. While some immunotherapies specifically target one (or a few) defined tumor-associated antigen(s), others operate in a relatively non-specific manner and boost natural or therapy-elicited anticancer immune responses of unknown and often broad specificity. Here, we propose a critical, integrated classification of anticancer immunotherapies and discuss the clinical relevance of these approaches

Supramolecular catalysis of 1,4-thiol addition by salophen-uranyl complexes

our catalysts mimic the behavior of a metalloenzyme, in that they bind 2-cyclopenten-1-one and promote reaction of the bound substrate. Release of the addition product, followed by preferential binding to another enone molecule, ensures the onset of a catalytic cycle with high turnover efficiency

Catalysis of the addition of benzenethiol to 2-cyclohexen-1-ones by uranyl-salophen complexes: a catalytic metallocleft with high substrate specificity

The base induced addition of benzenethiol to 2-cyclohexen-1-one and its 4, 4-, 5, 5- and 6,6-dimethyl derivatives is catalysed by a salophen-uranyl based metallocleft 2 in chloroform solution with high turnover efficiency and low product inhibition. Analysis of rate data coupled with equilibrium measurements for complexation of the catalyst with the enone reactants and addition products shows that the catalytic mechanism involves the three main steps typical of single-substrate enzymatic processes, namely substrate binding and recognition, transformation of the bound substrate, and release of the reaction product. Unlike the reference salophen-uranyl 1, catalyst 2 is endowed with a structured binding site responsible for a high degree of substrate specificity among the investigated enones, due to recognition of their shape and size

New insight into the mechanism of the conjugate addition of benzenethiol to cyclic and acyclic enones and of the corresponding uranyl-salophen-catalysed version

A thorough kinetic investigation of the triethylamine-catalysed addition of benzenethiol to 2-cyclopenten-1-one in chloroform shows that the highest energy transition state is a complex of thiol, enone, and base in a 1:1:1 ratio, but whether formation or disruption of the enolate-triethylammonium ion-pair intermediate is rate-limiting is uncertain. Intervention of a second thiol molecule in the assembly of the transition-state complex is ruled out, at least at thiol concentrations not exceeding 0.1-0.2 M. Thiol addition is accelerated significantly by uranyl-salophen complex 1 and its diphenyl derivative 2. The complicated kinetics are described to high precision by means of ad hoc integrated rate equations in which associations to the metal catalyst of the enone reactant and addition product are taken into account. The kinetics are consistent with a four-body transition-state complex, whose formation results from the reaction of a (weak) thiol-base complex with a (strong) enone-uranyl-salophen complex. Open-chain and cyclic enones react at similar rates and respond to the presence of metal catalyst in much the same way. The relative catalytic efficiencies of ethyldimethylamine, triethylamine, and quinuclidine are determined essentially by differences in base strength, rather than steric bulk, in both the presence and absence of a metal complex. Only with the use of the relatively bulky Hünigs base is an adverse steric influence apparent, which is particularly severe in the reaction catalysed by the sterically demanding 2

The uranyl unit as electrophilic catalyst of acyl transfer reactions

The kinetics of the base induced alcoholysis of a series of metallomacrocycles in which the salophen-uranyl unit is connected by polymethylene bridges of variable length to a pyrogallol monoacetate unit have been investigated in the MeO−Me4N+/MeOH and EtO−Me4N+/EtOH base-solvent systems. Analysis of rate data collected over a wide range of base concentrations, coupled with equilibrium measurements for complex formation between the alkoxide ion and the uranyl centre, showed that the ester cleavage processes are the results of two competing pathways involving alkoxide ion attack on uncomplexed and alkoxide-complexed substrates. Rate data related to the former pathway show that the proximal uranyl centre activates the ester carbonyl towards nucleophilic addition, thus behaving as an immobilized Lewis acid catalyst. The size of the acceleration critically depends on both solvent nature and distance of the ester function from the metal electrophile.\ud \u

MgCl2-based supports for the immobilization and activation of nickel diimine catalysts for polymerization of ethylene

Communication to the Editor - No Abstrac

MgCl2-based supports for the immobilization and activation of nickel diimine catalysts for polymerization of ethylene

Communication to the Editor - No Abstrac